Data: A look at Detroit’s rainiest, driest months, years between 1970-2020

Comparing annual, monthly rain totals over 50-year period for Detroit area

Photo by Anna Atkins on Unsplash (Unsplash)

DETROIT – Rain, rain, go away ... then come right back, because it’s only August and you’re nowhere near finished yet.

August can be a particularly rainy month, especially for regions swept up in hurricane season. Here in Michigan, August is pretty rainy, but it’s not quite the wettest month.

When looking at monthly rain totals for the Detroit area between 1970-2020, August, on average, was the fourth-rainiest month of the year. Can you guess what month sees the most rain in Detroit?

Let’s dive into some rain data for the last 50 years, gathered by the National Weather Service.


This article first appeared in our Data Drop Newsletter, where we tell important and fun stories using the facts and figures.


Detroit’s rainiest time of year

”April showers bring May flowers.” A common saying here in the Midwest.

And though it’s true, those May flowers do need those April showers -- April doesn’t bring nearly as much rain as you might think compared to the other months.

In fact, between 1970-2020, April was, on average, only the sixth-rainiest month of the year, recording an average of 3.069 inches of rainfall during that month each year.

The average rainiest month of the year, based on data from the last 50 years, was actually May. (If April showers bring May flowers, what do those extra May showers bring in June??)

The month of May saw a total of 174.74 inches of rainfall over the last 50 years, dropping an average of 3.426 inches during that month each year.

Here are the rainiest runner-ups:

  • June
    • Total rainfall from 1970-2020: 173.81 inches
    • Average June rainfall each year: 3.408 inches
  • July
    • Total rainfall from 1970-2020: 167.18 inches
    • Average July rainfall each year: 3.278 inches

Detroit’s driest time of year

For those of us familiar with Michigan winters, we know all too well that it’s often far too cold to see much rain. It’s mostly just snow, snow, ice, slush and more snow.

As you’ve probably assumed, Detroit’s coldest months -- December through February -- typically see the least amount of rain of the year.

The driest month, on average, between 1970-2020, was February. Over the 50-year period, the month of February recorded a total of 101.81 inches of rainfall, which is about an average of 1.996 inches of rain during that month each year.

January was the second-driest month on record, receiving a total of 102.94 inches of rainfall over the 50-year period, or an average of 2.018 inches of rain during that month each year.

October actually came in third place for driest month of the year, taking a sharp decline in rain totals between September and November (rain totals bounced back up in November). October saw a total of 121.74 inches of rain from 1970-2020 -- an average of 2.387 inches during that month each year.

Months, years with the most rainfall

Of all the rainy Mays between 1970-2020, the rainiest May of all was in 2004, when 8.46 inches of rain fell. May 2004 also happens to be the rainiest month ever during that 50-year time period, recording more rain than any other month of any other year.

July 2011 came in second place for rainiest month in 50 years, recording 7.66 inches of rainfall. September 1986 came in third with 7.52 inches of rainfall, and June 1987 came in fourth with 7.04 inches of rainfall.

The rainiest year of all was even more recent: 2011 recorded the most rainfall between 1970-2020, receiving a total of 47.7 inches of rain.

The following years came pretty close to 2011′s total:

  • 2018 recorded 43.81 inches of rain
  • 1990 recorded 42.64 inches of rain
  • 2000 recorded 42.18 inches of rain
  • 1985 recorded 40.08 inches of rain

Months, years with the least rainfall

The driest month of all the years was October of 2005, when only 0.13 inches of rain fell. That year saw a total of 28.3 inches of rainfall.

The absolute driest year between 1970-2020 was 1971, which only saw 22.79 inches of rain that entire year.

The following drier years came close to that rain total, too:

  • 1984 recorded 26.27 inches of rain
  • 2012 recorded 27.11 inches of rain
  • 1996 recorded 27.39 inches of rain
  • 1978 recorded 27.65 inches of rain

It’s interesting to note that just after 2011, the rainiest year of all the 50 years, the year 2012 was one of the driest the Detroit area has seen.

Check out the data yourself on the National Weather Service’s website right here.

The role of climate change

The data shows that annual rain totals have been increasing between 1970-2020 for the Detroit area -- and it’s likely that trend is not unique to our immediate region.

As the earth’s temperature gets warmer, so does the temperature of the oceans. Warmer oceans means more water is evaporating into the air, which leads to more precipitation. Environmental experts say that more intense precipitation, both in the form of rain and snow, is expected to become more common due to climate change, as global temperatures continue to rise.

Related reading: What Michigan’s future could look like without action on climate change


Previously on Data Drop:


About the Author:

Cassidy Johncox is a senior digital news editor covering stories across the spectrum, with a special focus on politics and community issues.